This invention relates to intermediates useful in the preparation of antibiotic compounds. In particular, it relates to chiral azetidinone intermediates useful in the asymmetric synthesis of .beta.-lactam antibiotics.
Many methods have been described for the preparation of .beta.-lactam antibiotics. One such method employs the so-called 2+2 cycloaddition of a ketene with an imine. Recently, considerable work has been directed to the asymmetric preparation of .beta.-lactam compounds with the cycloaddition method e.g., that of N. Ikota and A. Hanaki, Heterocycles, Vol. 22, No. 10, 1984, pp. 2227-2230. Furthermore, azetidinone intermediates have been previously used to produce isomers of cephalosporin antibiotics, Doyle et al., Can. J. Chem., 55, 484, 1977. A stereoselective process for preparation of .beta.-lactam antibiotics of the correct stereochemistry would be highly desirable in that cumbersome and expensive resolution steps could be avoided.